1. Field of the Invention
The present invention relates to a connector which connects a circuit board and a connecting object while allowing the circuit board and the connecting object to move relative to each other either in a common plane, in which the circuit board and the connecting object both lie, or in mutually parallel planes, in which the circuit board and the connecting object respectively lie, and relates to an LED lighting apparatus using the aforementioned connector.
2. Description of the Prior Art
Straight tube LED lighting apparatuses (LED lamps) are usually provided with a translucent tube, a plurality of circuit boards and a plurality of connectors. The translucent tube is formed as a linearly elongated hollow cylinder made of glass or plastic (e.g., polycarbonate). The plurality of circuit boards are planar in shape, arranged inside the translucent tube to lie in a common plane and aligned in the lengthwise direction of the translucent tube, and LEDs are fixed to one-side of the surfaces (undersurfaces) of the plurality of circuit boards. The plurality of connectors connect adjacent connectors of the plurality of connectors.
When the plurality of circuit boards are installed in the translucent tube, it is sometimes the case that adjacent circuit boards mutually deviate from their design positions in the aforementioned lengthwise direction or the widthwise direction of the translucent tube (directions orthogonal to the lengthwise direction). Therefore, the aforementioned connectors are required to have the capability of absorbing such positional deviations.
Patent Document 1 (Japanese Unexamined Patent Publication No. 2010-33953) discloses a connector having the capability of absorbing such positional deviations.
This connector is provided with a plurality of receptacle connectors (on-board connectors) which are fixed to one side of the surfaces of a plurality of circuit boards, respectively, and a plurality of plug connectors (coupling connectors), each of which connects two adjacent receptacle connectors of the plurality of receptacle connectors which are fixed to two adjacent circuit boards, respectively.
Each receptacle connector is provided with a receptacle insulator (housing) having an opening on one side thereof (on the opposite side of the receptacle insulator from the associated circuit board side), and a plurality of receptacle contacts (terminals) which are accommodated in the receptacle insulator in a state of facing the opening and which are each electrically connected to a circuit contained on the associated circuit board. Each receptacle contact has a pair of resilient lugs which are spaced from each other and face each other.
Each plug connector is provided with a plug insulator (housing), a plurality of plug contacts (coupling terminals) supported by the plug insulator therein, and an insulating plate which covers a surface of the plug insulator. The plug insulator is provided with a pair of support members and an elastically deformable connecting portion which connects the pair of support members. A plurality of support holes are formed through each of the pair of support members in the direction of thickness thereof. Each plug contact is provided with a linear columnar (prismatic-shaped) connecting portion and a pair of legs which respectively project from both ends of the columnar connecting portion in a direction orthogonal to the columnar connecting portion. One and the other of the pair of legs of each plug contact are inserted into a support hole of one support member of the pair of support members and a support hole of the other support member of the pair of support members from one side so that the end of each leg of each plug contact projects toward the circuit board side from the associated support hole. Each leg of each plug contact is rotatable within a slight angular range about its own axis with respect to the associated support hole, and a rotation of the leg causes the columnar connecting portion of the plug contact to rotate with respect to the associated support member. The insulating plate covers each support member from the opposite side of the pair of legs from the ends thereof to prevent each leg of each plug contact from coming off the associated support hole.
Bringing the pair of support members of each plug connector close to the two receptacle connectors fixed to two adjacent circuit boards, respectively, and inserting the pair of legs of each plug contact into the aforementioned opening of the receptacle insulator cause each leg of each plug contact to enter in between the pair of resilient lugs of the associated receptacle contact to thereby be resiliently held therebetween. As a result, the two adjacent circuit boards are electrically connected to each other via the plug connector and the two receptacle connectors. Therefore, if the connectors disclosed in Patent Document 1 are applied to an LED lighting apparatus such as described above, each circuit board is energized, which causes each LED to emit light.
In addition, if adjacent circuit boards deviate from each other in the lengthwise direction of the LED lighting apparatus from design positions, at least one leg of each plug contact slides with respect to the associated receptacle contact (the associated pair of resilient lugs thereof) while the aforementioned elastically deformable connecting portion is elastically deformed so as to change the distance between the pair of support members to thereby absorb the positional deviation.
On the other hand, if adjacent circuit boards deviate from each other in the widthwise direction of the translucent tube, at least one leg of each plug contact rotates with respect to the associated support hole (the aforementioned columnar connecting portion rotates with respect to the pair of support members) while the aforementioned elastically deformable connecting portion is elastically deformed so as to make the pair of support members slide relative to each other in the widthwise direction of the translucent tube to thereby absorb the positional deviation.
Since the plurality of LEDs and the plurality of connectors are fixed to circuit formation surfaces of the plurality of circuit boards (one side of the surfaces thereof), if the thickness of each connector is increased, the diffusive light that is emitted from the adjacent LEDs is partly intercepted by the connector, which narrows the illumination range (illumination angle) of light emitted from the LEDs. Accordingly, it is desirable that the height (thickness) of each connector be as small as possible.
However, in Patent Document 1, each plug contact has a structure in which the pair of legs of each plug contact project from the associated columnar connecting portion, and hence, the height of each plug contact increases by the amount of this projection.
Additionally, the pair of legs of each plug contact are lower in mechanical strength than the associated columnar connecting portion; however, since the pair of legs of each plug contact are made to contact (to be engaged with) the associated receptacle contact (the pair of resilient lugs thereof) in Patent Document 1, there is a possibility of each leg of each plug contact being distorted or damaged when the pair of legs of each plug contact and the associated receptacle contact are brought into contact with (are connected to) each other with a positional deviation therebetween. In addition, since the connector disclosed in Patent Document 1 is structured such that one or more legs of each plug contact rotate if the associated adjacent circuit boards deviate from each other in the lateral or rotational direction, repetitive positional deviations or vibrations applied to the connector causes the legs of each plug contact and the pair of resilient lugs of the associated receptacle contact to vibrate minutely, which may cause damage to the plating that is applied to the legs or the resilient lugs or makes the contact resistance therebetween easy to fluctuate. Therefore, the contact reliability between each plug contact and the associated receptacle contact easily deteriorates.
In Patent Document 1, since the plug contacts (the columnar connecting portions thereof) are exposed through the clearance between the pair of support members, even though surfaces of the support members of the plug insulator of the plug connector are covered by an insulating plate, there is a possibility of the plug contacts being distorted or sebum (from the hand) of an operator (user) being adhered to the plug contacts when the plug connector is plugged into the receptacle connector. Additionally, the exposure of the plug contacts through the clearance makes it easier for foreign matter such as dust to adhere to the plug contacts, which may become a cause of corrosion of the plug contacts or may cause sparking.